I found very interesting library for including vertex graphics into websites (eg for charts).
It uses SVG in newer browsers and VML in old IE so it works even in IE6. Graphics are DOM objects so after drawing they can be accessed by other JavaScript (event handlers).

Lately I read article about WebGL (can't find it now) but I realized that WebGL lack of support in browsers (many of them doesn't want to implement it). After that I probably stick to canvas for now and see how WebGL will work in the future (or play with other *GL on native platform). Interesting is idea to write WebGL and run it on mobile (Android): http://blogs.sonyericsson.com/developerworld/2011/02/24/webgl-support-in-the-android-web-browser/ I wonder how performance looks compared to native...